Quiet typewriter



March 2, 1954 Filed Dec. 29, 1950 my/V A f C- SCHRODER QUIET TYPEWRITER 2 Sheets-Sheet 1 CHM/@LES SCHRDP March 2, 1954 c. scHRoDER 2,670,834

QUIET TYPEWRITER Filed Deo. 29, 1950 Patented Mar. 2, 1954 QUIET TYPEWRITER Charles Schroder, West Hartford; Conn., assigner-V to :Underwood Corporation, New Y0rk,N. Y., a corporation of Delaware Application December 29, 1950, Serial No. 203,289

11 Claims. l

This invention relates to quiet-'typewritersand has 'forits principal object to provide a' typewriter in which vthe sounds made incident to the various operations of its mechanism are reduced to a noise level materially belowrthat heretofor obtained.

Another objectofithe invention is to provide` a novelcombination-of typewriter-base, mechanism-supporting .'frame, mask and muffler-casing orfenclosure .therefor'in such a cooperative relationias to reduce to a substantial extent the noises of'variousyfrequencies and magnitudes resulting fromzthedifl'erent impactsfincident to operation of Ithe typewriter mechanism.

The invention is in the nature of an improvement over the invention described'in my copend-y ing'application, Serial No. 134,703, filed December23, 1949, now =U. S. Patent No. 2,639,020, .to the end that the noise'of the typewriter isreduced to a negligible `level andjthe operation is so quiet asrto showan appreciable lowering of the noise level toa p oint under that ofthe present so-called noiseless typewriters. For-example, inrecent comparative#tests-madein an oflice where the usual noise levelof the room wasabout an average ofthat in various offices, the noiseless typewriter was audible' at a distance of about iive feet. whereas the'typewriter of the present invention wasaudible only at abouttwo and a half feet from the machine;

Other objects will be in part obviousvand in part` particularly pointed out'asthefollowing descriptionofL one embodiment of the invention proceeds.

In the drawings wherein` is represented oneof thefvarious possible: embodiments of the inventionz. l

Figure 1 is a frontvelevationalview of the quiet typewriter.embodyinguthe invention, portions beingV broken away to reveal various structural features,

Figure. 2..is aview incrosssection-taken substantially along'the median plane indicated by line 2`2 of Figurev iwith portions being broken away to vshow certain of the vibration-absorbing elements inlcentral section,

Figure 3 isla view in cross section similar to Figurez but talienon a line 3 3 of Figure l, and.

Figure i is a wiringdiagram of the circuit connections to the light andmotcr ofthe typewriter.

Referring now to the drawings and particularly to Figure the entire typewriter with the exception oi its keyboard'is enclosed within a casing or enclosure generally indicatedat l. The cas ing-includes alower section 8 andan upper section'or-cover 0 hinged thereto for opening to pro vide access to the-typewriter primarily for purposes' of inserting and' removing' the worksheet,

as well as making erasures in the typing. Ther typewriter forming the embodiment of the invention illustrated, is substantiallylike that shown and described in my copending application, Serial No. 134,703, led December 23, 1949, now U; S; Patent No. 2,639,020.` Said pending application. is directed to certain features embracedwthinl the usual'rnask or shell ofthey typewriter for damping or deadening sound vibrations. present invention these features cooperate with the outer enclosure or casing V1 to accomplish the` substantial overall noise reductions inithe opera... tion of the typewriter.

The typewriter comprises a metal ibase memberlil-of open rectangular form which hasxed; thereto a hand'rail` II surrounding and framing the keyboard of the typewriter. At eachv inner;- corner ofthe base -an'ear I2 is'provided to'which is attached a foot i3. Each foot I3, of which there are preferably four,l is received in a recess. or cavityv I4 formed in the bottomwall ofthelower section ofl casing L Each foot Iii-may, bev constructed substantially as shown inthe Lentz,v Patent No.v 2,549,692, issued-April 1'7195land comprises a metal cap I5a body of resilient.

material I6'such as rubber or neoprene,which has a reduced upper portion tting. the cap I5,A and an enlarged base portion I'I. The-base por tion I'I ts fairly snugly-into the recess I4..

Each ear I 2 has a recess 20 in which are mounted diaphragms 2l, Fig. 2, on which a skeleton frameY 22 is supported. Thev diaphragme` are composed of a central metal tube 23 to whichisi. vulcanized a web 24 of sound deadening material such asrubber and havingasize and density inV proportionto theload supported. thereby.V The.y

their ends to the side walls to form the complete frame. These includey a-cross bar 30 which p rovides a support for-an electric motor 3I which, its transmission devices indicated generally atv t?, drives the various operating mechanisms of;A the typewriter. the mounting for the platen carriage 34. Other cross bars 35, 3G, and 3l are provided, the first i' two respectively supporting theY key levers 38.*andi the type-bar actuating arms 39. Other units andl In' athe'.

Another cross bar 33 provides.

mechanisms, not shown, are also supported on the skeleton frame 22. These include the usual ribbon spools and associated ribbon feed and reversing mechanism, the ribbon vibrating mechanism, mechanisms for case shifting, letter feeding the carriage, and power-return of the carr1a e.

Igt will be noted that all of the working parts of the typewriter are supported on the skeleton frame 22, and this trarne in turn is supported solely on the sound damping diaphragms 2i. The resilience o the mounting aiorded by the diaphragms 2 i, under the vibratory effect of rapid operation of the various typewriter mechanisms, has the tendency to set up mechanical vibrations or the frame 22, which are objectionable particularly because they result in a vibratory movement or tilting of the carriage. To obviate these diiiiculties means are provided, as described in my said copending application, for limiting the amplitude of these vibrations or movements, Such means comprises adjustable cushion-stop devices ci, one at each side of the typewriter, adjacent the side walls 28. Each stop device includes a screw i2 threaded in an ear i3 on the base is, the head of the screw having a coil spring adapted to engage, but normally free of, a lug it at each end of the cross bar 3l. The screws i2 are `adjusted so that there is a slight clearance between the spring end and lug d4.- The kclearance is such as not to allow the vibrations or movements to` exceed the maximum permissible amplitude. Thus, as the frame 22 sets up mechanical vibrations or tilting movements, these'are checked and regulated to an extent to greatly minimize the objectionable results.

The skeleton frame 22' and the mechanisms supported thereby are covered and enclosed in large part by a mask which, in relation to the casing or outer-enclosure l, forms an inner shell closely encasing the operating mechanisms of the typewriter. This mask comprises a front wall it which, as shown in Fig. 2, curves upwardly toward the rear to blend into a top wall, and further comprises a rear wall il and two side walls lit, one of which is shown in Fig. l. As indicatedzat t9, Figs. l and 2, the walls Q5, l, 48 of the mask are lined with a layer of sound absorbing material such as telt.

As etere-mentioned, the upper section or cover 9 of the casing l is hinged at 5l along a rear juncture of the lower and upper sections 8, il. Upon being released by operation of a latching device later described, the cover il is automatically raised by a spring-powered raising device 52, see Fig. 3, which is substantially like that fully disclosed in the Lindburg Patent No. 1,603,781. This device comprises a bracket E3 secured to the lower section e and holding a shaft on which a slotted arm 5d is mounted for rocking movement. A torsional spring 55 surrounding said shaft tends to swing the arm 54 in a clockwise direction. A tension-adjusting device in the form of a worm-and-gear mechanism 56, 5? and arranged between the arm 5t and the spring 55, affords adjustment of the force of spring 55 so that it is just ample to raise the cover without harsh action. The arm 54 has av slot in which a post 58 operates, the post being mounted on the cover t to transmit the raising force` of the arm cli thereto. As the cover 9 reaches its fully open position, as determined by the post reaching. the leitward end of the slot in arm 5e, a pair of leaf springs converging toward each other at said end impart a snub- 4 bing action to post 58, which brings the cover quietly to a stop at open position.

Referring to Fig. 3, the cover-latching device comprises a bracket et secured to the cover s and on which is hook-shaped latch El is pivoted. A spring 52 tensions latch 5l to swing clockwise to a position determined by a stop S3 on said bracket. To hold the cover 9 in its closed position, the latch 6i hooks under a lug 54 on the lower section t. The latch is swung rightward to release its hook from lug ed by the camming action of a release bar t5. The upper end of said bar has a bevel adapted to coact with a stud 6E on the latch Si. At its upper end the release bar 55 is slidably guided in a slotted member El and its lower end is articulated to a lever arm 58. The arm 63 at its leitward end is secured to a stub shaft t9 which is journaled in and projects through a wall portion lil of the lower section 8. At its other end the stub shaft 69 has secured thereto a lever ll which carries a palm key l2. For convenient access by the typist, the palm key 'i2 is arranged adjacent the typewriter keyboard just outside the hand rail l i. Depressing the palm key 'it will cause lever 'il and arm 68 to rock about the axis of stub shaft 59, and thus raise the release bar to cause its beveled end to cam the latch iii out of engagement with lug Eil. Upon release of said latch the action of the cover-raising device 52 will cause the cover 9 to be quickly and silently raised. For convenience in closing the cover against the force of the raising device 52, a handle 'HS is provided at the front of the cover.

As illustrated in Fig. l, the lower section 8 has a width, from its bottom upward a major portion of its depth, which is slightly greater than the width oi the machine at the base lll and mask side walls 43. The space between vthe side walls 48 and the adjacent walls of the lower section affords room for grasping the machine for lifting it out. The upper portion of section 8 and the entire upper section 9 are of such width end to end as to allow the platen carriage 34 to travel the full extent in each direction, the width of a major portion of the lower section to about a minimum as shown, the typewriter ts readily in the usual place on standard. secretarial desks.

The adjoining edges of the lower andupper sections 3, e meet in abutting relation. To assure a tight, soundproof closure all said edges are bound by a rubber or flexible plastic strip 'l5 having a channel which straddles and closely nts the marginal portions of each section. The two anges of the strip T5 are connected by a curved wall i6, and a web 1'? adjacent said wall and spanning said flanges forms a shallow tubular section with wall .I'i. This tubular section affoi-ds a resilience that assures a soundproof juncture with the opposite edge strip 'i5 or with another surface, as later mentioned.

It may be here noted with reference to Figs. l and 2 that the iront wall l of the typewriter mask or inner shell forms the wall of the muffler casing 'l at that region. v This has the advantage of making certain control elements in wall @6 accessibleA without complicating the 'structure of the casing 'l in order to have said elements brought out thru a second wall. These control elements include a bichromc ribbon selector knob 8@ and a motor switch knob 8i by which the motor 3l is controlled. lt should also be noted that the mask wall fit ranges upwardly beyond the height of the lowercasing section 8 and.

By keeping terials havingeithera porous or'bious chair-- at'er mayfbeused` as afsu'itable acoustical insulaiti'or'il however, igoodres'ults' areobtained by'al matted glass wool material known commercially* as-"l'iberglas.` This mtaerial in` a one inch free thickness ilis recommended, thesarne to beicomprsse'd to about inch thickness when installed."

Th'i'slsh'eetmatrial maybe' cut into mats to t the"various1`separate vareas ofv the casing "I a'n'd'f may fbe'lcovered with -af cloth "material if desired. Eachmat'thus formed may besecured, aslby" cementin'g,v tothe interiorsurfacesof thecas- As'shown" in Fig.' 2, the bottom'area of thei' lowerfsection Bha's a'layer of sound-'insulatf ingffm'aterial of lesser-"thickness applied thereto; afcotton felt being foundsuitable'for' this pur p's." The 'lower' surface of 'said 'area' may also have'a layerof felt applied thereto. l

Tov prevent the leading'or vtrailing 'edges ofthe paper-on the'platen carriage 34 from catching? the insulating material 8201 its cloth covering;V the-'casingeover 9 has 'af sheet'metal defiecto'r`81f lining same.' This deflector 'covers thea-rea above: and" to the 'rear' offthe platencarriage 34,' and? provides' a vtrough 88 which preventsthepaper frci'm` becoming mutilated by' engaging projec#Vv tions at" the' back f of lthe typewriter' a's the oar; ria'gertravels. The"trough.88" extends therfull'Y length of carriage'travel'in eachdirection'andi` thus guides thepaper smoothly.' over theshallow end portionsiof thelowe'r vcasing section 8; Theviv defle'ctor 81' is fsecured to the cover v9 by'V screws threafdedinto' postsl 89 on the cover;A a" rubber' washer being inserted between4 ther screw head' and` the deector;

The typistiob'serves'theprogressof the work through a? window '9provided`in the'cover sec" tion S To" prevent'thetransmission of sound" waves therethrough;v said window preferably' comprises two layers ofglas'sr separated by marf gin'al 'stripsj Sincethe' usual room illumination isv shaded' from' the' typing sheet by the' casingcover"9"inits"closed position; `the typewriter pro-- vides itsownlillumiriation, .preferably in thel form' ofa'v fluorescent light 8| Theflight 9| is mounted" bysuitablefmeansontheinterior of the coversg ina" position `immediately l`'above fand slightlyv fory wardof'theftypewriterfplaten and preferably coextensiveiwitli'thewindowl A switch'SZ, later described; -ismounted on the cover' S'a'nd controls 'i the currenttotheflight 9|.

For supplying electric current to both the motor 3| and the fluorescent light 9|, the typewriter unit with casing 1` may be wired in accordance with the circuit shown in Fig. 4, assuming that alternating current is used. The switch 92 is of the usual well-known type used where the starting of the uorescent bulb is effected manually by manipulatingthe switch. The conm', trol elementV in this type of switch is ma'nipu-` latable to three positions, namely oli "on,`" and "start, progressing from left to right in the 'order given. This switch comprises two normally open' switches as shown, both of which are closed when thec'o'n'trol element'is moved to start"'position'.

and the upperwone" of gwhich -stays closed when thesaid element is movedto on position. Although the motor has its own switch 8 l, it is preferable lto have the switch 92 control --both the iiuorescent'light and the motor, so that the typist need usually operate only the one switch. From the' circuit wiring between the fluorescent bulb l and switch S2, connections 93 and 9c are made,- by which current is directed to the motor 3l when switch 92 is either inv its start or "on position, assuming motor switch 8l to be closed.- The circuit to the fluorescent light Si includes the usual ballast $5, and condenser 96.

-To avoid running an extension cord through the wall` of the casing 1, for supplying electric current to the light Si and motor 3 l, an adaptor iixture 55. Fig. 3, is provided. Said fixture cornprises an outlet box 99 attached to a rear wall of the lower casing section 8, which wall has an opening mi! in which the receptacle unit of an extension cord, not shown, is inserted for coupling to a two-prong connector it! secured in the box. A receptacle iii?. at the front oi' the box 99 is adapted to receive a plug 03 of an extension cord, the wires of which are connected to the motor 3 i, one wire including the switch 8 i, From the terminals of the two prongs of connector -lll connections are made to the fluorescent light 9! and its switch B2, as well as the ballast and condenser units 95 and 96, said connections being made as shown in the wiring diagram, Fig. 4. The plug and receptacle connection |82, |93 afforded by the adaptor fixture e3 enables convenient detachment of the extension cord to the typewriter motor and and removal of parts for .service or replacement.

.The provision of the two-prong connector lill enables detachment ofthe extension oord from the entire typewriter unit when desired. Prim'arily, however, the adaptor iixture 93 enables making the necessary connections from the current supply to the casing and from said casing to'the typewriter motor 3l andiiuorescent light circuit without requiring an actual opening in thev casing l thru which the extension cord may eX- tend. Thus, the full extent of the quieting eiect of the casing 'l is assured by the adaptor fixture 98 in that said fixture obviates the necessity for. any thru opening in the casing to aiord a pas- Y sage for the usual extension cord.

f'The following table shows the results of noise level tests conducted on the three typewriters noted. In tests A and B the same typewriter was used;l except that in test B the typewriter was constructed in `accordance with the present invention. In all three tests the typewriters were supported on a stand. The various machine op.- erations given in the table are self explanatory, except Regular Virite which consists of typing two lines of text, the text .being the same in each instance. All readings are 'in decibels,l

l Test-A Test B Test C Electric Electric A i Typewriter, Typewriter, Sin-mgl applic., Ser. prescrit ',lvolfistr No. 134,703 Application D Db Db Db Regular Write.. 67 5 6l Case Shlth. 5S 52 63 2 Tabulation 66 60 62 Spacc'ilar 62- n54 59 Line vSpace 7l 62 62 Back Space 59 52 60 idling.- 42 41 th-us facilitates assembly Cai - A compari-son oiv the readings in tables A andB shows the great reduction 1n noise level afforded by the improvements of the present inventionl over that of the typewriter of the application Serial No. 134,703. Of particular signiiicance is the -drop of l1 decibles in the Regular Write In making these comparisons it should be noted i that the decibel unit is a ratio or logarithmicY valuev and, as such, should not be compared mere,- ly on the basis of numerical quantity diierences. While these differences in the decibel readings are in most cases appreciable, the audible differences perceptible to impressive. v

What is claimed is:

l. In a typewriting machine, in combination, typing instrumentalities including a keyboard, a set of type bars and a platen carriage, a skeleton frame supporting said typing instrumentalities, a base, resilient sound-damping means mounting said frame on the base, said frame being capable of vibratory and tilting movements as an incident to rapid operations of the machine and due to the resilience of said mounting means,

a mask substantially enclosing the typing instru-I mentalities excepting the keyboard andA platen carriagagmeans supporting said mask in stable relation to said base, a casing having sound-insulating walls and housing said base and said.

a-base having foot means, resilient sound-damping means mounting said frame on the base, said frame being capable of vibratory and tilting movements as an incident to rapid operations of the machine and due to the resilience of said mounting means, a mask substantially enclosing the typing instrumentalities excepting the keyboard and platen carriage, means supporting said mask instable relation to said base, a casing having sound insulating walls and housing said base and said mask and said platen carriage throughout its range oi travel but exposing said keyboard, said= casing dening an opening thru which vsaid keyboard extends for operationoutside the casing, and the casing being in contact with the'remainder of the typewriting machine only at the borders of said .opening and the foot meansof said base.

3. In a typewriting machine, in combination, typing instrumentalities including a keyboard, a set of type bars and a platen carriage, a skeleton frame supporting said typing instrumentalities, a base, means mounting said frame on the base comprising a plurality of sound-damping diaphragms, said framebeing capable of vibratorythe human ear are far more supported .byj said base andl substantially enclostypewriter with the front wall of its mask sub- ,ing the typing instrumentalities Iexcepting the stantially foi-ward of the frontwall of the lower keybQaldandepiaten Calfliage, 2 Casing having section, said casing also including a hinged upper 1- Sound insulating Walls-and housing said base and section having depending walls meeting the up- ,saidmaskfand-said platen. carriage vthi'oughoiu': ,5 standing walls of said lower section, the sides its range of travel-but exposing Sadkeyboal'd, of said opening'pressing against the side areas saidcasingdening an opening thru which said of `said mask, the portion of said cover section ing, and the edges of the casing defining the sides wardly in close` overlying relation to the juncture of the Opening having pressure contact with said m `of the front and top walls of said mask.

mask and base. 7. In a typewriting machine, in combination,

4.,In a typewrting machine, in @Ombinatiom typing instrumentalities including a keyboard typing insitlumentalites including a keyboard, a set of type bai-s and a platen carriage, a fa' set of type bars and a platen Carriage, Si Skeieskeleton frame .supporting said typing instru- .t0n fanl Supporting Said typing instlumental is mentalities, a mask substantially enclosing the ties.v a base, resilient mund-damping means typing insti'umentalities excepting the keyboard `mllntng Said frame 0n vthe bas. Said frame and the platen carriage, means including resilient .being capable of vibratory and tilting movements sound-damping diaphragms supporting said as an incident t0 rapid peltiOnS 0f the maCnine skeleton frame, said frame. being capable offviand due to the resilience of said mountingmeans, 2,) bratory and tilting movements incident toirapid enclosing the typing instrumentalities excepting of Said dmphmgms, me

sound-insulating walls and housing said base ent-1y of the Skeleton frame, the last sa a mask supported by said base and Substantially' operations of the machine due to the resilience ans supporting .saidfdiathe keyboard and platen carriage, a casing having phmgms and supporting said mask independid supnnd Sad mask and Sai-d Diten Carriage through" 2,-, porting means including foot elements having visaid mask to form a soundproof joint at said housing said mask and said platen .carriage having a pressure contact with the side areas of edges.

5 A Soundploof 235mg fol housing a type* tends, the casing front wall .edges which denne the lsides of the opening having a rm contact with the side areas of the mask to form a soundproof joint at said edges, said foot elements resting on the casing door and forming the support for the mask within the casing. frontwall andtop Wall JOlnd by a Curved por 8. In a typewriting machine, in combination, typing instrumentalities including a keyboard and a set of type bars and a platen carriage, a skeleton frame supporting said typing' instrusaid openinor slanting forwardly and downwardly neanmcluding foot elements having Vibratiom immediately over and in tangential relation to Saugarluchltnsmgt anzid yet afforlmg. a

the curved portion of said mask between its front 55 y upp a a casmg avmg and top Walls a door and sound-insulating walls and housing 6. In a typewriting machine, in combination, dlgkonad giaggasllgllhrug typing instiumentalities including a keyboard g In a typewriter in combination a skeleton top wall, a casing having sound-insulating walls and housing said base and said mask and said TG name havmg mounted thereon typmg mst'uplaten carnage throughout lts range of travel mentalities including a keyboard and a set of said casing comprising a lower section adapted type bals and a platen Carnage, means fOr drivto recelve the typewnter therem and havmg uping said type bars and foi ielativeiy case shiftwall dening an opening adapted to admit the 75 the platen carriage, said means comprising a trolling the' various mentalities ing said type bars silience of said motor and transmission devices mounted on said skeleton frame; a mask substantially enclosing the driving means and the typing instrumentalities excepting the keyboard and the platen carriage; means including resilient sound-damping diaphragms supporting said skeleton frame; said frame, due to the resilience of said diaphragms, being capable of vibratory and tilting movements incident to rapid operations of the typing instrumentalities; means supporting said diaphragms and supporting said mask independently o the skeleton frame; a casing having sound-insulat- 'ing walls and housing substantially the entire typewriter keyboard, said casing an opening through excepting the having a front wall defining which said keyboard extends, the front wall edges defining the opening having a firm contact with said mask to form a soundproof joint at said edges, the keyboard having elements for conoperations of the typing instrumentalities including that of moving the platen carriage.

10. In a typewriter, in combination, a skeleton frame having mounted thereon typing instruincluding a keyboard and a set of type bars and a platen carriage; means for drivand for relatively case shifting the type bars and the platen and for moving the platen carriage, said means comprising a motor and transmission devices mounted on said skeleton frame; a mask substantially enclosing the typing instrumentalities excepting the' keyboard and the platen carriage; means including resilient sound-damping diaphragms supporting said skeleton frame; said frame,

diaphragms, being capable of vibratory and tilting movements incident to rapid operations of the typing instrumentalities; means supporting said diaphragms and supporting said due to the remask independently of the skeleton frame; the last said supporting means including foot elements having vibration-absorbing characteristics and yet aording a substantially rigid support; and a casing having a floor and sound-insulating walls and housing substantially the entire typewriter except the keyboard, said casing havring a iront wall defining an opening through which said keyboard extends, the iront wall edges defining the opening having a rrn contact with said mask to form a soundproof joint at said edges, said foot elements resting on the casing floor to support the typewriter inthe casing, the keyboard having elements for controlling the various operations of the typing instrumentalities including that of moving the platen carriage. 11. A noiseless electric typewriter having a skeleton frame and an electric motor, platencarriage, type actions and operating keys mounted on said frame, a base having slip resistant feet and a plurality of resilient diaphragms on which the skeleton frame is mounted, mask means for the skeleton frame mounted on the base and comprising walls spaced from the skeleton frame and the said parts mounted thereon, a casing having means for deiinitely locating the base with the operating keys in iront of the casing and having means for sealing the mask `when the base is so located, a movable cover for said casing having means for further sealing the mask, and electrical connections from the electric motor to the exterior of the casing.

CHARLES SCHRODER.

References Cited in the file of this patent UNITED STATES PATENTS Name Waldheim Date July 21, 1925 Number 

